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Cerrar SIS
Pantalla anterior
Producto: NO SE HA ESCOGIDO NINGUN EQUIPO
Modelo: NO SE HA ESCOGIDO NINGUN EQUIPO
Configuracin: NO SE HA ESCOGIDO NINGUN EQUIPO
Operacin de Sistemas 773D & 775D TRUCKS AIR SYSTEM &
BRAKES
Nmero de medio -SENR1412-00 Fecha de publicacin -31/01/1996
Fecha de actualizacin -03/11/2006
SENR14120001
Systems Operation
IntroductionNOTE: For specifications with illustrations, make
reference to the Specifications for 773D Trucks & 775D Trucks;
Air System And Brakes; SENR1411. If the Specifications in SENR1411
are not the same as listed in the Systems Operation, Testing &
Adjusting, look at the printing date on the front cover of each
book. Use the Specifications listed in the book with the latest
date.
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SchematicsAir System Schematic(1) Air compressor governor. (2)
Air compressor. (3) Air dryer. (4) Air pressure relief valve. (5)
One-way check valve. (6) Service air reservoirs. (7) Drain
valve.
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(10) Relay valve [for rear wheel brakes]. (11) Relay valve [for
front wheel brakes]. (12) Double check valve. (13) Double check
valve. (14) Inversion valve. (15) Front wheel brake valve (ON-OFF).
(16) Pressure protection valve. (17) Retarder brake control valve.
(18) Parking and secondary brake control valve. (19) Service brake
control valve. (21) Secondary brake control valve. (22) Front wheel
brake master cylinder. (23) Rear wheel brake master cylinder. (24)
Parking brake control valve (ON-OFF). (25) Windshield wiper motor.
(26) Windshield wiper control valve. (27) Horn valve. (28)
Secondary air reservoir [for parking and secondary brake]. (29) Air
horn. (30) Front brake ratio valve. (31) Automatic Retarder Control
Valve (ARC) [Attachment]. (A) Air Pressure Switch [For Retarder
Brake]: Switch is normally open, closed by air pressure.
When this switch is closed, it activates the retarder brake
indicator on the instrument panel.
(C) Air Pressure Switch [Stop Lamp For Rear Brakes]: Switch is
normally open, closed by air pressure.
When this switch is closed, it activates the brake lamp relay
which activates the stop lamps.
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(D) Air Pressure Switch [Parking and Secondary Brake Signal For
Transmission Control]: Switch is normally open, closed by air
pressure.
When this switch is open, it activates the Parking/Secondary
Brake ON indicator on the Caterpillar Electronic Monitoring System
(CEMS) panel via Cat Datalink. This switch also allows for rapid
shifting of the transmission.
(E) Air Pressure Switch [Retarder And Service Brake Signal For
Transmission Control]: Switch is normally closed, opened by air
pressure.
When this switch is open, it activates the brake retarder
indicator at the transmission control. This will signal the
transmission control when a higher engine rpm is needed for
upshifts or downshifts of the transmission.
(F) Sensor [For Brake Air Pressure]: Sensor sends a signal to
the CEMS control to input for the Brake Air Pressure gauge. When
air pressure is too low, the sensor also triggers the master fault
light and fault alarm.
Schematic Key:
(G) Standard Air Lines. (H) Automatic Retarder Control Valve
(ARC) (31) Air Lines [Attachment].
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Hydraulic System Schematic
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(18) Parking and secondary brake control valve. (33) Lockup
solenoid. (34) Selector piston [for lockup clutch]. (35) Load
piston [for lockup clutch]. (36) Pressure reduction valve. (37)
Lockup clutch and solenoid valve group. (38) Modulation reduction
valve [for lockup clutch]. (40) Relief valve [for parking brake
release system]. (41) Passage [to rear wheel brakes]. (42) Inlet
relief valve [for torque converter]. (43) Torque converter. (44)
Oil cooler [for torque converter and brakes]. (45) Oil pump drive.
(46) Parking brake release oil filter. (47) Torque converter oil
filter. (48) Lockup clutch [for the torque converter]. (49) Screen.
(50) Parking brake release section [of oil pump]. (51) Torque
converter charging section [of oil pump]. (52) Torque converter
scavenge section [of oil pump]. (53) Scavenge screen. (54) Left
rear wheel brake. (55) Right rear wheel brake. (56) Hydraulic oil
tank.
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(57) Line [for torque converter and brake cooling return]. (58)
Oil pump [for hoist hydraulics and rear brake cooling]. (59)
Suction screen. (60) Oil cooler relief valve [for rear brakes].
(61) Control valve [for hoist hydraulics]. (62) Return oil screen
[for hoist hydraulics]. (63) Suction screen. (P) Pressure tap [for
pilot oil]. (R) Pressure tap [for parking brake release oil]. (S)
Pressure tap [for torque converter lockup clutch]. (T) Pressure tap
[for torque converter outlet]. (U) Pressure tap [for brake cooler
outlet]. (V) Pressure tap [for parking brake release oil]. (W)
Pressure tap [for torque converter inlet]. (X) Pressure tap [for
brake cooler inlet]. (Y) Pressure tap [for left rear brake oil
cooling inlet]. (Z) Pressure tap [for right rear brake oil cooling
outlet]. (AA) Pressure tap [for left rear brake oil cooling
outlet]. (BB) Pressure tap [for right rear brake oil cooling
inlet].
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Brake System Schematic
(22) Front wheel brake master cylinder. (23) Rear wheel brake
master cylinder. (40) Relief valve [for parking brake]. (54) Left
rear wheel brake assembly. (55) Right rear wheel brake assembly.
(64) Front wheel brake assemblies. (65) Line [to makeup oil tank].
(66) Air chamber of the front wheel brake master cylinder. (67) Air
line [from the front brake relay valve]. (68) Line [to the makeup
oil tank]. (69) Air line [from the rear brake relay valve].
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(70) Air chamber of the rear wheel brake master cylinder. (71)
Hot oil from the brake housing going to hydraulic tank. (72) Slack
adjuster [for the service brakes]. (73) Oil line [from the oil
cooler for the left and right rear brake]. (74) Hot oil from the
brake housing going to hydraulic tank. (75) Oil line [from park
brake release section of the oil pump]. (76) Air line [to the
parking brake control valve]. (77) Check valve.
Location Of ComponentsCab Brake Control Group
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Top View (15) Front wheel brake valve (ON-OFF). (16) Pressure
protection valve. (17) Retarder brake control valve. (9) Service
brake control valve. (21) Secondary brake control valve. (28)
Secondary air reservoir. (30) Front brake ratio valve.
Side View (15) Front wheel brake valve (ON-OFF). (16) Pressure
protection valve. (19) Service brake control valve. (21) Secondary
brake control valve. (28) Secondary air reservoir. (30) Front brake
ratio valve.
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Chassis Brake Control Group
Top View (1) Air compressor governor. (2) Air compressor. (3)
Air dryer. (6) Service air reservoirs. (10) Relay valve [for rear
wheel brakes]. (11) Relay valve [for front wheel brakes]. (14)
Inversion valve. (18) Parking and secondary brake control valve.
(22) Front wheel brake master cylinder. (23) Rear wheel brake
master cylinder. (56) Hydraulic oil tank.
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Side View (1) Air compressor governor. (3) Air dryer. (6)
Service air reservoirs. (10) Relay valve [for rear wheel brakes].
(11) Relay valve [for front wheel brakes]. (14) Inversion valve.
(22) Front wheel brake master cylinder. (23) Rear wheel brake
master cylinder. (56) Hydraulic oil tank.
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Front Service Brake Lines Group
Top View (22) Front wheel brake master cylinder. (56) Hydraulic
oil tank. (78) Brake make-up oil tank.
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Side View (22) Front wheel brake master cylinder. (56) Hydraulic
oil tank. (78) Brake make-up oil tank.
Rear Service Brake Lines Group
Top View (18) Parking and secondary brake control valve. (23)
Rear wheel brake master cylinder. (46) Parking brake release
oil
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filter. (50) Parking brake release section [of oil pump]. (56)
Hydraulic oil tank. (72) Slack adjuster. (78) Brake make-up oil
tank. (79) Diverter valve.
Side View (18) Parking and secondary brake control valve. (23)
Rear wheel brake master cylinder. (46) Parking brake release oil
filter. (50) Parking brake release section [of oil pump]. (56)
Hydraulic oil tank. (72) Slack adjuster. (78) Brake make-up oil
tank. (79) Diverter valve.
Brake Cooling Lines
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Top View (44) Oil cooler [for torque converter and brakes]. (49)
Screen. (50) Parking and secondary brake release section [of oil
pump]. (51) Torque converter charging section [of oil pump]. (52)
Torque converter scavenge section [of oil pump]. (56) Hydraulic oil
tank. (57) Line [for torque converter and brake cooling return].
(59) Suction screen [inside hydraulic oil tank]. (60) Oil cooler
relief valve [for rear brakes (inside hydraulic oil tank)]. (61)
Control valve [for hoist hydraulics (inside hydraulic oil tank)].
(63) Suction screen [inside hydraulic oil tank]. (U) Pressure tap
[for brake cooler outlet]. (X) Pressure tap [for brake cooler
inlet]. (Y) Pressure tap [for left rear brake oil cooling inlet].
(Z) Pressure tap [for right rear brake oil cooling outlet]. (AA)
Pressure tap [for left rear brake oil cooling outlet]. (BB)
Pressure tap [for right rear brake oil cooling inlet].
Caterpillar Electronic Monitoring System (CEMS)The Caterpillar
Electronic Monitoring System (CEMS) consists of an action alarm, an
action light and a monitoring panel with individual alert
indicators for each machine system listed on the CEMS panel.
The CEMS is designed to alert the operator of an immediate or
impending problem in one or more of the machine systems.
Instrument Panel (1) Brake Air Pressure gauge. (2)
Parking/Secondary Brake ON indicator.
Brake Air Pressure gauge (1) and Parking/Secondary Brake ON
indicator (2) are part of the instrument panel. Brake Air Pressure
gauge (1) is controlled by a sensor. Parking/Secondary Brake ON
indicator (2) is controlled by a pressure switch. Brake Air
Pressure gauge (1) displays the air pressure in the system. When
the needle on Brake Air Pressure gauge (1) is in the red area, the
CEMS action light will come on and the master alarm will
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sound. This warning comes on when the air pressure from the
service reservoirs is below 483 kPa (70 psi). Parking/Secondary
Brake ON indicator (2) flashes while the parking brakes or the
secondary brakes are engaged or a brake master cylinder has over
stroked. When the parking brake or the secondary brake is engaged
and the transmission is moved into gear, the CEMS action light will
come on and the master alarm will sound.
When the cut-out air pressure is at 830 kPa (120 psi) and the
lever on the parking brake control valve is in the OFF position,
Parking/Secondary Brake ON indicator (2) will stop flashing and the
parking and secondary brakes will release.
Air Compressor Governor
Air Compressor Governor (1) Spring [to set pressure]. (2)
Piston. (3) Inlet and exhaust valve. (4) Spring [for inlet and
exhaust valve].
The air compressor governor operates with the air compressor
unloader pistons to control the air pressure in the system. The air
compressor governor has a cut-out pressure setting of 830 35 kPa
(120 5 psi). When the air system increases to the maximum setting,
the air pressure from the service air reservoirs flows through the
opening of the governor. This air flow moves the governor piston
(2) against the force of spring (4). Piston (2) moves inlet and
exhaust valve (3) to open the inlet opening. The air pressure flows
through the governor to operate the compressor unloader mechanism
which stops the flow of compressed air.
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When the air pressure in the service air reservoirs decreases to
the minimum setting of 690 + 0 - 35 kPa (100 + 0 - 5 psi), the
force of spring (1) is greater than the minimum pressure on piston
(2). Inlet and exhaust valve (3) moves to close the inlet opening
and open the exhaust opening of the governor. This permits the
compressor to send compressed air flow to the service air
reservoirs.
Air Compressor
Air Compressor (1) Air compressor governor. (2) Air
compressor.
Air compressor (2) is driven by the timing gear train on the
rear of the engine and is lubricated by the lubrication system for
the engine. Air compressor (2) is cooled by the engine cooling
system. Air for air compressor (2) comes from the engine air inlet
manifold. Air compressor governor (1) is mounted on air compressor
(2) and connects to the air dryer.
Air Dryer
Air Dryer (1) Air dryer. (2) Air relief valve.
Air flows from the air compressor into air dryer (1). Air dryer
(1) removes the moisture and contaminants from the air system. Air
relief valve (2) located on air dryer (1) protects the air system
from damage. Air relief valve (2) will open at 1200 kPa (175 psi).
Air relief valve (2) can not be adjusted.
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Air ReservoirsService Air ReservoirsThere are three air
reservoirs in the air system. The service air reservoirs hold air
under pressure for control of the service brakes and retarder. The
secondary air reservoir holds air under pressure for control of the
parking brake and secondary brakes.
(1) Service air reservoirs [for service brakes and retarder].
(2) Air pressure relief valve. (3) Drain valve.
Service air reservoirs (1) are located on top of the hydraulic
and transmission tank. A cover must be removed to access them. The
two service air reservoirs (1) are connected; one has air pressure
relief valve (2) and the other has drain valve (3). Air pressure
relief valve (2) is a backup to the relief valve on the air dryer
to protect the air system from damage. Air pressure relief valve
(2) will open at 1030 kPa (150 psi). Moisture drains from one air
reservoir to the other. By opening manual drain valve (3), the
moisture is expelled.
Secondary Air Reservoir
Location of Secondary Air Reservoir (For Parking and Secondary
Brakes).
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Location of Drain Valve (For Secondary Air Reservoir).
The secondary air reservoir is located at the rear of the cab. A
cover must be removed to access the secondary air reservoir. The
drain valve is located on the right side of the cab. By opening the
manual drain valve, moisture is expelled.
One-Way Check Valve
Components Of The Check Valve (1) Seat. (2) Valve. (3)
Spring.
The one-way check valves in the air system are used to stop the
reverse flow of air from the air reservoirs. There are one-way
check valves fastened in the inlet of the first service air
reservoir and in the inlet of the secondary air reservoir.
Air from the air compressor will put spring (3) in compression
and valve (2) will open. This permits air to flow into the
reservoirs.
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When the air pressure in the reservoir and the force of spring
(3) is more than the air pressure from the air compressor, valve
(2) will move against seat (1). This prevents air from flowing into
the air compressor from the reservoirs.
Pressure Protection Valve
Pressure Protection Valve (1) Supply passage. (2) Valve. (3)
Delivery passage.
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A pressure protection valve in the air system prevents a
complete loss of air pressure in either the secondary air system or
any accessory device.
All air flow for the accessory circuits for the brakes must flow
through the pressure protection valve. Air will not flow through
valve (2) until the air pressure at supply passage (1) is 550 kPa
(80 psi). When the pressure at supply passage (1) is 550 kPa (80
psi), valve (2) moves to allow air to flow to delivery passage (3).
Valve (2) closes when the air pressure lowers below 485 kPa (70
psi).
Service Brake Control ValveGradual modulation of the service
brake system is controlled by the use of the foot operated brake
control valve (treadle). The rate of rise (time versus psi) is
called modulation. The foot valve modulates air pressure from the
service air reservoirs to the brake relay valve. In addition, the
valve body serves as a junction point for the several circuits
requiring non-modulated air/auxiliary components and the retarder
brake controls.
Service Brake Control Valve (Treadle) (1) Seat. (2) Rubber
spring. (3) Piston assembly. (4) Retainer. (5) Outlet passage. (6)
Spring. (7) Valve seat. (8) Valve seat. (9) Valve. (10) Valve body.
(11) Valve spring. (12) Exhaust passage. (13) Inlet passage. (14)
Exhaust diaphragm.
When the brake pedal is pushed, a force is put on seat (1). This
force pushes rubber spring (2) and piston assembly (3) down. Valve
seat (7) closes exhaust passage (12) in valve (9). Piston assembly
(3) moves valve (9) off valve seat (8). Pressure air from inlet
passage (13) flows around valve (9) to outlet passage (5). The air
then flows to the relay valve for the air chambers in the brake
master cylinders.
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When the air pressure below piston assembly (3) becomes more
than the force above the piston, the piston lifts enough to allow
valve (9) to move up to valve seat (8). This stops the supply of
pressure air. Piston assembly (3) is still in contact with valve
(9), so exhaust passage (12) is also closed. The service brake
control valve is now in balance. Air pressure is held in the lines
and in the air chambers in the brake master cylinders.
When the pedal is lifted a small amount, the force above piston
assembly (3) is less. The pressure air below piston assembly (3)
and the force of spring (6) lifts the piston off valve (9).
Pressure air in the lines and in the air chambers in the brake
master cylinders flows around piston assembly (3), through exhaust
passage (12) and out exhaust diaphragm (14) until the forces above
and below the piston are in balance.
When the pedal is completely released, piston assembly (3) moves
off valve (9). Air pressure opens exhaust diaphragm (14). Valve (9)
is held against valve seat (8) by spring (11).
Parking And Secondary Brake Control ValveThe parking and
secondary brake control valve is located on the right side of the
truck frame across from the hydraulic oil tank. The parking and
secondary brake control valve controls the flow of oil to the rear
parking brakes.
The parking brakes are spring applied and pressure released.
Location of Parking and Secondary Brake Control Valve.
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Parking And Secondary Brake Control Valve In ON Position (1)
Passage [from parking brake release section of the oil pump]. (2)
Relief valve. (4) Piston. (5) Air inlet passage. (6) Stem. (7)
Chamber [connected to torque converter inlet relief valve]. (8)
Drain passage [to hydraulic oil tank]. (9) Check valve. (10)
Spring. (11) Oil outlet passage [to release parking brakes].
When the parking brake control valve in the cab is in the
Parking Brake ON position, air flow to air inlet passage (5) will
be blocked. When there is no air flow at air inlet passage (5),
spring (10) will keep stem (6) pushed up and stop the flow of oil
from passage (1) to oil outlet passage (11). The engine must be in
operation to have brake oil pressure to passage (1).
Parking And Secondary Brake Control Valve In OFF Position (1)
Passage [from parking brake release section of the oil pump]. (2)
Relief valve. (4) Piston. (5) Air inlet passage. (6)
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Stem. (7) Chamber [connected to torque converter inlet relief
valve]. (8) Drain passage [to hydraulic oil tank]. (9) Check valve.
(10) Spring. (11) Oil outlet passage [to release parking
brakes].
Move the parking brake control valve in the cab to the Parking
Brake OFF position. Air pressure will be allowed to flow into
passage (5). Air pressure will force piston (4) and stem (6) down.
When stem (6) moves down, the pressure oil from passage (1) enters
oil outlet passage (11). The oil pressure will increase in the
brake housing and release the parking brakes. Relief valve (2)
limits system pressure to 4690 200 kPa (681 29 psi).
Front Wheel Brake Valve (On-Off) And Parking Brake Control Valve
(On-Off)The front brakes are caliper disc brakes. An ON-OFF valve
on the left side of the instrument panel, in the cab, permits the
operator to turn OFF the air to the front brakes when they are not
needed.
When the front wheel brake valve is in the ON position,
modulated air from the service brake control valve activates the
front and rear brakes. When the front wheel brake valve is in the
OFF position, air from the service brake control valve will only
flow to the rear brakes.
The front wheel brake valve should be ON except when operating
conditions are such that all wheel brakes are not needed. Move the
lever to the OFF position when only rear wheel brakes are
needed.
The parking brake control valve (ON-OFF) for the rear brakes is
not modulated. It is located on the transmission control console in
the cab. The rear brakes are oil cooled multi-disc brakes.
When the parking brake control valve is in ON position, no air
flows to the parking and secondary brake control valve. This causes
parking brake application. When the parking brake control valve is
in the OFF position, full air system pressure flows to the parking
and secondary brake control valve. This causes parking brake
release.
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Control Valve Components (1) Plunger. (2) Lever. (3) Passage [in
plunger]. (4) Exhaust passage. (5) Delivery passage. (6) Spring.
(7) Inlet valve. (8) Seat. (9) Spring. (10) Supply passage.
The operation of the front wheel brake valve (ON-OFF) and the
operation of the parking brake control valve (ON-OFF) are the same.
When air is needed to flow through the valve, lever (2) depresses
plunger (1). Plunger (1) moves inlet valve (7) off of seat (8) and
exhaust passage (4) is closed. Pressure air flows into supply
passage (10) and flows around inlet valve (7), which is off seat
(8). Air flows out through delivery passage (5). When air is not
needed to flow through the valve, lever (2) releases plunger (1).
Spring (6) moves plunger (1) up and inlet valve (7) is pushed up to
seat (8) by spring (9). Air from delivery passage (5) flows through
passage (3) in plunger (1) to exhaust passage (4).
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Front Brake Ratio Valve
Location Of Front Brake Ratio Valve
The front brake ratio valve controls the air pressure to the
front brakes when the front wheel brake valve (ON-OFF) is in the ON
position. When the service brake pedal is partially depressed and
the supply air pressure is below 448 kPa (65 psi), only 50% of the
supply air pressure is allowed to the front wheel brake master
cylinder. When the supply pressure to the front brake ratio valve
reaches 448 kPa (65 psi) and above, the delivery pressure to the
front wheel brake master cylinder equals the supply pressure.
With the air flow restricted during partial engagement, the rear
brakes will engage first and provide more control to the operator.
During full supply air pressure, the operator will receive maximum
braking capacity.
Retarder Brake Control Valve
Location Of Retarder "ON" Light On The Instrument Panel
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A hand control valve on the right side of the steering column
provides modulated application of the service brakes for the rear
wheels when machine retarding is needed. There is a retarder "ON"
light on the instrument panel.
Location Of Retarder Brake Control Valve
The retarder brake control valve is under the dash. The handle
is connected to the retarder brake control valve by a shaft
assembly.
Retarder Brake Control Valve (1) Cam. (2) Piston. (3) Valve seat
[for exhaust air]. (4) Spring. (5) Valve seat [for inlet air]. (6)
Supply passage. (7) Delivery passage. (8) Exhaust passage.
The hand operated retarder brake control valve modulates air
pressure, up to a maximum of 550 kPa (80 psi), to the rear brake
relay valve. When the handle is in the OFF position, air at system
pressure at supply passage (6) is stopped by the inlet valve.
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When the handle is moved to the ON position, spring (4) is put
in compression by cam (1). Spring (4) puts pressure on piston (2)
and the piston is moved down against the exhaust end of the valve
assembly. The exhaust end of the valve assembly is held on seat (3)
and the inlet end of the valve assembly is off seat (5). Supply air
flows past the inlet end of the valve assembly to delivery
passage
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